I can answer for my site (https://docalysis.com/) which does a semantic search to figure out which parts of the document are most relevant. Then you just use those parts.
Docalysis also shows you the PDF side-by-side, has page numbers, and overall responses are of better quality according to users that have emailed comparisons to ChatPDF.
Docalysis also shows you the PDF side-by-side, has page numbers, and overall responses are of better quality according to users that have emailed comparisons to ChatPDF.